1. Field of the Invention
The present invention relates to a resist processing apparatus and resist processing method and, more particularly, to a developing apparatus and developing method in which, e.g., a developing solution is supplied onto a photoresist layer formed on the surface of a semiconductor wafer to perform a developing process.
2. Description of the Related Art
In the manufacture of semiconductor devices, a photoresist is applied to a semiconductor wafer serving as an object to be processed. A circuit pattern is transferred on the photoresist using a photolithography technique and developed to form a circuit.
For example, in this developing process, the following system is generally employed. That is, a developing solution is supplied from a developing solution supply nozzle to a semiconductor wafer serving as an object. The developing solution is held by its surface tension in a swelled manner for a predetermined period of time to develop a circuit pattern.
In recent years, from the viewpoint of uniformly supplying a developing solution, a paddle type system is employed as this general system. In this paddle type system, for example, a developing solution supply nozzle having a large number of nozzle holes aligned in a line is used. A developing solution is supplied from this nozzle, while a semiconductor wafer is rotated at a low speed to spread the developing solution on the entire semiconductor wafer.
In the use of such a system, a method of feeding a developing solution in a tank with nitrogen gas to the nozzle under pressure is employed. This method has the problem of bubble formation in swelling the developing solution on a semiconductor wafer. The presence of bubbles generates a portion where the developing solution is not supplied, undesirably generating a non-developed portion.
To solve this problem, a method of deaerating a developing solution in a vacuum (Jpn. UM Appln. KOKAI Publication No. 62-37923), and a method of removing bubbles in a developing solution using a foam breaker (Jpn. Pat. Appln. KOKAI Publication No. 61-259523) have been proposed.
In the above method of deaerating a developing solution in a vacuum which is disclosed in Jpn. UM Appln. KOKAI Publication No. 62-37923, the concentration of the developing solution undesirably changes upon evaporation of water in the developing solution. In addition, with recent micropatterning of circuit patterns, some resists have higher performance, i.e., higher resolution. Even small bubbles which have not posed any problem cause a developing error with such resists. Once formed, small bubbles cannot be sufficiently removed by the conventional deaeration methods.